Centrifugal Blower

ABSTRACT

A centrifugal blower includes a centrifugal fan and a partition cylinder portion. The centrifugal fan includes first blades and second blades arranged about a fan central axis. The partition cylinder portion has a cylindrical shape extending in an axial direction. A diameter of the partition cylinder portion expands in the axial direction. The partition cylinder portion is located inside the second blades in the radial direction. The partition cylinder portion partitions, on an airflow upstream side of the first blades and the second blades, air drawn into spaces between the first blades from air drawn into spaces between the second blades. A length of each first blade in the radial direction is larger than a length of each second blade in the radial direction.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2018-058947 filed on Mar. 26, 2018.

TECHNICAL FIELD

The present disclosure relates to a centrifugal blower.

BACKGROUND

A general centrifugal blower of this type includes a centrifugal fan configured to simultaneously draw two airflows separated from each other.

SUMMARY

According to an aspect of the present disclosure, a centrifugal blower includes: a centrifugal fan including a plurality of first blades arranged about a fan central axis, and a plurality of second blades arranged about the fan central axis, the plurality of second blades being located on a first side of the plurality of first blades in an axial direction of the fan central axis and being aligned to the plurality of first blades; and a partition cylinder portion having a cylindrical shape extending in the axial direction, a diameter of the partition cylinder portion expanding in the axial direction toward a second side that is an opposite side of the first side; the partition cylinder portion being located inside the plurality of second blades in a radial direction of the centrifugal fan. The centrifugal fan is configured to rotate about the fan central axis to: take in air from the first side into spaces between the plurality of first blades and spaces between the plurality of second blades; blow out the air in the spaces between the plurality of first blades outward in the radial direction; and blow out the air in the spaces between the plurality of second blades outward in the radial direction. The partition cylinder portion partitions, on an airflow upstream side of the plurality of first blades and the plurality of second blades, the air taken into the spaces between the plurality of first blades through an inside of the partition cylinder portion in the radial direction from the air taken into the spaces between the plurality of second blades through an outside of the partition cylinder portion in the radial direction. A length of each first blade of the plurality of first blades in the radial direction is larger than a length of each second blade of the plurality of second blades in the radial direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings; in which:

FIG. 1 is a cross-sectional diagram schematically illustrating a cross-section of a centrifugal blower taken by a plane including a fan central axis, according to a first embodiment;

FIG. 2 is an enlarged view of II part of FIG. 1;

FIG. 3 is a cross-sectional diagram of first blades taken along line of FIG. 2;

FIG. 4 is a cross-sectional diagram of second blades taken along IV-IV line of FIG. 2;

FIG. 5 is a cross-sectional diagram schematically illustrating a centrifugal blower of a second embodiment taken by a plane including a fan central axis and corresponding to FIG. 1;

FIG. 6 is a cross-sectional diagram schematically illustrating a centrifugal blower of a third embodiment taken by a plane including a fan central axis and corresponding to FIG. 5; and

FIG. 7 is a cross-sectional diagram schematically illustrating a centrifugal blower of a modification example of the third embodiment taken by a plane including a fan central axis and corresponding to FIG. 6.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described hereinafter referring to drawings. In the embodiments, a part that corresponds to a matter described in a preceding embodiment may be assigned with the same reference numeral, and redundant explanation for the part may be omitted. When only a part of a configuration is described in an embodiment, another preceding embodiment may be applied to the other parts of the configuration. The parts may be combined even if it is not explicitly described that the parts can be combined. The embodiments may be partially combined even if it is not explicitly described that the embodiments can be combined, provided there is no harm in the combination.

A centrifugal blower is known, which includes a centrifugal fan configured to simultaneously draw two airflows separated from each other, and a first radial band that separates the air blown out of the centrifugal fan into an airflow on one side and an airflow on the other side in an axial direction.

The centrifugal fan has multiple blades arranged about a rotation shaft. The first radial band has an annular shape and is located at a center part of the blades in the axial direction of the centrifugal fan.

The centrifugal blower includes a separation cylinder that has an approximately circular cylinder shape and is located inside the centrifugal fan in a radial direction. The separation cylinder does not rotate and partitions an air intake passage extending from an intake port to the centrifugal fan into two passages.

In the centrifugal blower, since a blade partition panel that is a first radial band is provided at a center part of the blade in the axial direction of the centrifugal fan, a first part of the blade located on a first side of the blade partition panel closer to the air intake port in the axial direction has the same shape as a second part of the blade located on a second side of the blade partition panel farther from the air intake port in the axial direction.

In the air passages defined between the blades, the air passing through the outside of the separation cylinder flows into the air passages located on the first side of the blade partition panel, and the air passing through the inside of the separation cylinder flows into the air passages located on the second side of the blade partition panel. Accordingly, in the centrifugal blower, there may be room for enlarging a part of the blades of the centrifugal fan located on the second side inward in the radial direction.

In the centrifugal fan, if the length of the blade in the radial direction is increased, the length of the blade in the axial direction can be decreased by the increased length in the radial direction for obtaining a specific fan performance. That is, in the centrifugal blower, since the shape of a part of the blade on the first side of the blade partition panel is the same as the shape of a part of the blade on the second side of the blade partition panel, there may be room for miniaturizing the centrifugal fan in the axial direction.

The present inventors have though that the length of the blade in the axial direction on the second side of the blade partition panel may be decreased by enlarging the blade outward in the radial direction. The above points are recognized as a result of detailed consideration by the present inventors.

Embodiments are described below with reference to the drawings. In the following embodiments, identical or equivalent elements are denoted by the same reference numerals as each other in the figures.

First Embodiment

A centrifugal blower 10 (hereinafter, simply referred to as a “blower 10”) of the present embodiment is used in an air-conditioner for a vehicle. The blower 10 separates multiple airflows and blows air. As shown in FIGS. 1, 2, the blower 10 includes a centrifugal fan 12, a partition cylinder portion 14, a fan casing 16, a partition panel 18, an upstream partition wall 20, and a motor 22.

The centrifugal fan 12 is a multi-layer centrifugal fan that rotates about a fan central axis CL to draw multiple airflows separated from each other from one side in an axial direction DRa of the fan central axis CL. In the present embodiment, the axial direction DRa is the axial direction DRa of the fan central axis CL, i.e. the axial direction DRa of the centrifugal fan 12, the radial direction DRr is the radial direction DRr of the fan central axis CL, i.e. the radial direction DRr of the centrifugal fan 12. A circumferential direction is the circumferential direction about the fan central axis CL, i.e. the circumferential direction of the centrifugal fan 12.

The motor 22 is a driving source that rotates the centrifugal fan 12 in a predetermined fan rotation direction RT (see FIG. 3). The motor 22 includes a motor body 221 fixed to the fan casing 16 and a motor rotation shaft 222 protruding from the motor body 221 to the one side in the fan axial direction DRa. The motor rotation shaft 222 and the centrifugal fan 12 that is linked to the motor rotation shaft 222 so as not to rotate relative to the motor rotation shaft 222 rotate in the fan rotation direction RT in response to an energization to the motor 22.

The centrifugal fan 12 includes multiple first blades 121 arranged about the fan central axis CL, multiple second blades 122 arranged about the fan central axis CL, a separation panel 123, a main panel 124, and a side panel 125. The first blades 121, the second blades 122, the separation panel 123, the main panel 124, and the side panel 125 are integrated with each other, and accordingly they rotate together about the fan central axis CL.

In the centrifugal fan 12, multiple first blades 121 constitute a first blowing portion 12 a that sends air using the first blades 121, and multiple second blades 122 constitute a second blowing portion 12 b that sends air using the second blades 122. The second blades 122 located on the one side of the first blades 121 in the fan axial direction DRa. That is, the second blowing portion 12 b is located on one side of the first blowing portion 12 a in the fan axial direction DRa to be layered.

Each of the first blades 121 has a first end 121 a that is an end on one side in the fan axial direction DRa, and a second end 121 b that is an end on the other side in the fan axial direction DRa. Each of the second blades 122 has a first end 122 a that is an end on the one side in the fan axial direction DRa, and a second end 122 b that is an end on the other side in the fan axial direction DRa.

The main panel 124 of the centrifugal fan 12 has a circular disk shape extending in the fan radial direction DRr. A motor rotation shaft 222 is connected to a center part of the main panel 124. The second end 121 b of the first blade 121 is fixed to the main panel 124 at a part that is located on a radially outer side compared to the connection part of the main panel 124 and the motor rotation shaft 222.

Since the first blades 121 and the second blades 122 are provided in such manner, the centrifugal fan 12 takes in air from the one side in the fan central axis DRa and discharges the intake air radially outward by rotating about the fan central axis CL. In detail, the centrifugal fan 12 rotates about the fan central axis CL to take in air from the one side in the fan axial direction DRa into the spaces between the first blades 121 and the spaces between the second blades 122. Simultaneously, the centrifugal fan 12 blows out the intake air in the space between the first blades 121 and the space between the second blades 122 radially outward.

Taking in air into the space between the first blades 121 corresponds to taking in air into the first blowing portion 12 a. Similarly, taking in air into the space between the second blades 122 corresponds to taking in air into the second blowing portion 12 b. Blowing out the intake air in the space between the first blades 121 radially outward corresponds to blowing out the intake air in the first blowing portion 12 a outward in a radial direction of the first blowing portion 12 a. Similarly, blowing out the intake air in the space between the second blades 122 radially outward corresponds to blowing out the intake air in the second blowing portion 12 b outward in a radial direction of the second blowing portion 12 b.

The separation panel 123 of the centrifugal fan 12 has a circular annular shape surrounding the fan central axis CL and has a plate shape extending in the fan radial direction DRr. The separation panel 123 is located between the first blades 121 and the second blades 122 in the fan axial direction DRa. Accordingly, the first end 121 a of the first blade 121 and the second end 122 b of the second blade 122 are fixed to the separation panel 123. That is, the first end 121 a of the first blade 121 is a connected end joined to the separation panel 123, and the second end 122 b of the second blade 122 is also a connected end joined to the separation panel 123.

In detail, the separation panel 123 has a width in the fan radial direction DRr enough to be connected to entire part of the first end 121 a of the first blade 121 and the second end 122 b of the second blade 122. In the present embodiment, the length of the first end 121 a of the first blade 121 is larger than the length of the second end 122 b of the second blade 122. The separation panel 123 extends in the fan radial direction DRr to cover the entire part of the first end 121 a of the first blade 121. The separation panel 123 extends inward and outward from the second blade 122 in the fan radial direction DRr.

According to this configuration, the separation panel 123 partitions the air flowing through the space between the first blades 121 from the air flowing through the space between the second blades 122, and prevents the airs from mixing together. The air flowing through the space between the first blades 121 corresponds to air in the first blowing portion 12 a. The air flowing through the space between the second blades 122 corresponds to air in the second blowing portion 12 b.

The side panel 125 of the centrifugal fan 12 has a circular annular shape about the fan central axis CL. The first ends 122 a and neighboring parts of the second blades 122 are connected to the side panel 125.

Each of the first blades 121 has a first leading edge 121 c that is an upstream edge located upstream with respect to the airflow in the space between the first blades 121. Each of the first blades 121 has a first trailing edge 121 d that is a downstream edge located downstream with respect to the airflow in the space between the first blades 121. That is, the first leading edge 121 c defines a part of an inlet of an air flow passage defined between the first blades 121, and the first trailing edge 121 d defines a part of an outlet of the air flow passage.

Similarly, each of the second blades 122 has a second leading edge 122 c that is an upstream edge located upstream with respect to the airflow in the space between the second blades 122. Each of the second blades 122 has a second trailing edge 122 d that is a downstream edge located downstream with respect to the airflow in the space between the second blades 122. That is, the second leading edge 122 c defines a part of an inlet of an air flow passage defined between the second blades 122, and the second trailing edge 122 d defines a part of an outlet of the air flow passage. For example, since the outlet of the air flow passage defined between the second blades 122 is located on the other side of the side panel 125 in the fan axial direction DRa, the second trailing edges 122 d are also located on the other side of the side panel 125 in the fan axial direction DRa.

The partition cylinder portion 14 has a cylindrical shape extending along the fan axial direction DRa, and a diameter of the partition cylinder portion 14 enlarges toward the other side in the fan axial direction DRa. Specifically, the partition cylinder portion 14 has a cylinder portion 141 and an expanded portion 142 integrated with the cylinder portion 141. The partition cylinder portion 14 is located inside the second blades 122 in the fan radial direction DRr, i.e. inside the second blowing portion 12 b.

The cylinder portion 141 of the partition cylinder portion 14 has a cylindrical shape extending along the fan axial direction DRa. In detail, the cylinder portion 141 has a circular cylindrical shape whose axis is the fan central axis CL and extends in the fan axial direction DRa.

The expanded portion 142 of the partition cylinder portion 14 extends from the cylinder portion 141 toward the other side in the fan axial direction DRa, and the diameter of the expanded portion 142 enlarges toward the other side in the fan axial direction DRa. In detail, the diameter of the expanded portion 142 expands toward the other side in the fan axial direction DRa such that the other end of the expanded portion 142 extends outward in the fan radial direction DRr.

The air flowing inside the cylinder portion 141 in the fan radial direction DRr is drawn into the space between the first blades 121. The air flowing outside the cylinder portion 141 in the fan radial direction DRr is drawn into the space between the second blades 122. That is, the partition cylinder portion 14 partitions the air flowing into the space between the first blades 121 from the air flowing into the space between the second blades 122 on the airflow upstream side of the blades 121, 122.

The partition cylinder portion 14 of the present embodiment continues from a radially inner part of the separation panel 123 of the centrifugal fan 12 and is integrated with the centrifugal fan 12. Therefore, the partition cylinder portion 14 rotates together with the centrifugal fan 12. The radially inner part of the separation panel 123 in the fan radial direction DRr is connected to the expanded portion 142 of the partition cylinder portion 14. In detail, the expanded portion 142 of the partition cylinder portion 14 extends inward in the fan radial direction DRr from the radially inner part of the separation panel 123.

The expanded portion 142 may correspond to an inward extending part 126 of the centrifugal fan 12 extending inward in the fan radial direction DRr from the separation panel 123. That is, the partition cylinder portion 14 includes the inward extending part 126 that is a part of the centrifugal fan 12. The inward extending part 126 is located inside of both the first blades 121 and the second blades 122 in the fan radial direction DRr. In detail, the inward extending part 126 is located inside of both the first end 121 a of the first blade 121 and the second end 122 b of the second blade 122 in the fan radial direction DRr.

The fan casing 16 is a non-rotating member that does not rotate and is a casing that accommodates the centrifugal fan 12. The fan casing 16 includes a bell mouth portion 161 that is an air intake portion defining a casing air intake port 16 a through which the air is taken into the centrifugal fan 12. The bell mouth portion 161 defines a rim of the casing air intake port 16 a of the fan casing 16. The cross-section of the bell mouth portion 161 has an arc shape such that the air outside the fan casing 16 smoothly flows into the casing air intake port 16 a.

The casing air intake port 16 a is located on the one side in the fan axial direction DRa with respect to the centrifugal fan 12, and opens in the fan axial direction DRa.

The cylinder portion 141 of the partition cylinder portion 14 is located inside the bell mouth portion 161 in the fan radial direction DRr. In the casing air intake port 16 a, a part inside the cylinder portion 141 in the fan radial direction DRr is a first air intake port 16 b, and a part outside the cylinder portion 141 in the fan radial direction DRr is a second air intake port 16 c. Accordingly, the second air intake port 16 c is an opening having a circular annular shape surrounding the first air intake port 16 b.

The air flowing into the fan casing 16 through the first air intake port 16 b is drawn into the first blowing portion 12 a through the radially inner side of the cylinder portion 141 of the partition cylinder portion 14. The air flowing into the fan casing 16 through the second air intake port 16 c is drawn into the second blowing portion 12 b through the radially outer side of the cylinder portion 141 of the partition cylinder portion 14.

The fan casing 16 includes a fan surrounding portion 162, and the fan surrounding portion 162 defines a fan surrounding space 162 a surrounding the centrifugal fan 12. The air blown out of the centrifugal fan 12 flows into the fan surrounding space 162 a.

The partition panel 18 having a plate shape whose thickness direction corresponds to the fan axial direction DRa is provided in the fan surrounding space 162 a. The partition panel 18 is located radially outside the centrifugal fan 12 to have a small gap with the centrifugal fan 12, and the partition panel 18 has an annular shape extending along an outer circumference of the centrifugal fan 12. A radially outside end of the partition panel 18 is fixed to the fan surrounding portion 162.

The partition panel 18 provided as described above partitions the fan surrounding space 162 a into a first flow-out passage 162 b and a second flow-out passage 162 c located on the one side of the first flow-out passage 162 b in the fan axial direction DRa.

The air flowing through the space between the first blades 121, i.e. a first air flowing radially outward from the first blowing portion 12 a, flows into the first flow-out passage 162 b. The air flowing through the space between the second blades 122, i.e. a second air flowing radially outward from the second blowing portion 12 b, flows into the second flow-out passage 162 c.

The partition panel 18 is provided to suppress the first air from flowing into the second flow-out passage 162 c and to suppress the second air from flowing into the first flow-out passage 162 b. Specifically, a position of a radially inner end 18 a of the partition panel 18 is aligned to a position of a radially outer end 123 a of the separation panel 123 of the centrifugal fan 12 in the fan axial direction DRa. The first air is not necessarily completely prevented from flowing into the second flow-out passage 162 c, but it is enough that the first air flowing into the second flow-out passage 162 c is reduced. This also is the same as the second air flowing into the first flow-out passage 162 b.

The first flow-out passage 162 b is a scroll passage that guides the air flowing out of the first blowing portion 12 a in the fan circumferential direction to flow out of the blower 10. Similarly, the second flow-out passage 162 c is a scroll passage that guides the air flowing out of the second blowing portion 12 b in the fan circumferential direction to flow out of the blower 10. The air flowing out of the first flow-out passage 162 b and the air flowing out of the second flow-out passage 162 c flow through different air passages partitioned from each other, even outside the blower 10, for example.

A duct 24 for guiding the air to the blower 10 is provided on the one side in the fan axial direction DRa with respect to the fan casing 16, and the duct 24 is joined to the fan casing 16 on the one side in the fan axial direction DRa. An upstream air passage 24 a guiding the air to the casing air intake port 16 a is defined inside the duct 24. The upstream air passage 24 a is located upstream of the first air intake port 16 b and the second air intake port 16 c with respect to the airflow and is connected to the first air intake port 16 b and the second air intake port 16 c.

A filter 26, the upstream partition wall 20, and a front filter partition wall 28 is provided in the upstream air passage 24 a. The upstream partition wall 20 is another member separated from the partition cylinder portion 14 and fixed to the duct 24 or the fan casing 16, for example. That is, the upstream partition wall 20 is a non-rotating member.

The upstream partition wall 20 is provided on the one side in the fan axial direction DRa with respect to the cylinder portion 141 of the partition cylinder portion 14, and has a cylindrical shape aligned to the cylinder portion 141 in the fan axial direction DRa. For example, the upstream partition wall 20 of the present embodiment has a circular cylindrical shape coaxial with the cylinder portion 141 of the partition cylinder portion 14, and a radius of the upstream partition wall 20 is the same as that of the cylinder portion 141. According to such configuration, the upstream partition wall 20 partitions an air flowing into the radially inner side of the cylinder portion 141 from an air flowing into the radially outer side of the cylinder portion 141 on the upstream side of the cylinder portion 141.

Since the upstream partition wall 20 is the non-rotating member and the partition cylinder portion 14 rotates together with the centrifugal fan 12, the upstream partition wall 20 is slightly spaced from the cylinder portion 141 so as not to contact the cylinder portion 141 of the partition cylinder portion 14. The gap between the partition cylinder portion 14 and the cylinder portion 141 is small such that the air on the radially inner side of the upstream partition wall 20 and the air in the radially outer side on the radially outer side of the upstream partition wall 20 are mixed with each other.

The filter 26 is a non-rotating member fixed to the duct 24, for example, and allows the air to flow to a downstream side after filtrating the air. For example, the filter 26 includes nonwoven fabric as a main element.

The filter 26 is located on the one side in the fan axial direction DRa with respect to the upstream partition wall 20. Since the filter 26 is located upstream of the upstream partition wall 20 with respect to the airflow, the filter 26 filtrates the air flowing toward the centrifugal fan 12. In detail, the filter 26 filtrates both the air flowing toward the first blowing portion 12 a of the centrifugal fan 12 and the air flowing toward the second blowing portion 12 b.

The upstream partition wall 20 extends to the filter 26 along the fan axial direction DRa. The upstream partition wall 20 may extend to contact the filter 26 or to a position close to the filter 26 to have a small gap between the upstream partition wall 20 and the filter 26.

The front filter partition wall 28 is located on the one side in the fan axial direction DRa with respect to the filter 26 in the duct 24, and the front filter partition wall 28 has a cylindrical shape aligned to the upstream partition wall 20 across the filter 26. In the present embodiment, the front filter partition wall 28 has a circular cylindrical shape coaxial with the upstream partition wall 20, and a radius of the front filter partition wall 28 is the same as that of the upstream partition wall 20.

The front filter partition wall 28 extends on the other side in the fan axial direction DRa to the filter 26. Accordingly, a large part of the air flowing through an radially inner side of the front filter partition wall 28 flows into the radially inner side of the upstream partition wall 20 through the filter 26. A large part of the air flowing through an radially outer side of the front filter partition wall 28 flows into the radially outer side of the upstream partition wall 20 through the filter 26.

As shown in FIGS. 3, 4, the shape of the first blade 121 is different from the shape of the second blade 122. Specifically, as shown in FIGS. 2, 3, the first blade 121 are backward-curved blade that is positioned on the side opposite to the fan rotation direction RT toward the outer side in the fan radial direction DRr. The first blades 121 may curve against the fan rotation direction RT. That is, the shape of a turbofan is adopted as the shape of the first blades 121, and the first blowing portion 12 a is a turbofan.

In contrast, as shown in FIGS. 2, 4, the second blade 122 is forward-curved blade that is positioned on the forward direction side in the fan rotation direction RT toward the outer side in the fan radial direction DRr. The second blades 122 may curve in the fan rotation direction RT. That is, the shape of a sirocco fan is adopted as the shape of the second blades 122, and the second blowing portion 12 b is a sirocco fan.

As shown in FIGS. 3, 4, the number of the first blades 121 is different from the number of the second blades 122. Specifically, an angle between the first blades 121 having a common endpoint (fan central axis CL) is larger than an angle between the second blades 122 having a common endpoint (fan central axis CL). The intervals between the first blades 121 may be larger than the intervals between the second blades 122. That is, the number of the first blades 121 is smaller than the number of the second blades 122.

In the present embodiment, the first blades 121 and the second blades 122 are different in shape as follows. As shown in FIGS. 1, 2, an inner diameter D1 i of the first blades 121 whose center is the fan central axis CL is smaller than an inner diameter D2 i of the second blades 122. The inner diameter D1 i is a diameter of an imaginary circular cylinder whose center is the fan central axis CL and which contacts the first blades 121 on the radially inner side in the radial direction. That is, the inner diameter D1 i is a diameter of an imaginary circular cylinder whose center is the fan central axis CL and which is inscribed to the first blades 121. The inner diameter D2 i of the second blades 122 can also be explained in the same way. An outer diameter D2 o of the second blades 122 is smaller than an outer diameter D1 o of the first blades 121. The outer diameter D1 o is a diameter of an imaginary circular cylinder whose center is the fan central axis CL and which contacts the first blades 121 on the radially outer side in the radial direction. That is, the outer diameter D1 o is a diameter of an imaginary circular cylinder whose center is the fan central axis CL and which is circumscribed to the first blades 121. The outer diameter D2 o of the second blades 122 can also be explained in the same way.

As it can be understood from the differences between the inner diameters D1 i, D2 i and between the outer diameters D1 o, 02 o, a length L1 r of the first blade 121 in the fan radial direction DRr is larger than a length L2 r of the second blade 122 in the fan radial direction DRr. The length L1 r of the first blade 121 is a radial width of the first blade 121 in the fan radial direction DRr, and the length L2 r of the second blade 122 is a radial width of the second blade 122 in the fan radial direction DRr. Accordingly, the length L1 r of the first blade 121 can be calculated, as shown in FIGS. 1, 2, from the following expression: L1 r=(D1 o−D1 i)/2. The length L2 r of the second blade 122 can be calculated from the following expression:

L2r=(D2o−D2i)/2.

As shown in FIG. 2, a height HF1 of the first leading edge 121 c in the fan axial direction DRa is smaller than a height HF2 of the second leading edge 122 c. Further, a height HB1 of the first trailing edge 121 d in the fan axial direction DRa is smaller than a height HB2 of the second trailing edge 122 d. That is, the first blade 121 is larger in the fan radial direction DRr and smaller in the fan axial direction DRa as compared to the second blade 122. The first blades 121 and the second blades 122 are different in shape as described above.

Next, the airflow in the blower 10 will be roughly described below. When the motor 22 rotates the centrifugal fan 12 in the fan rotation direction RT, a first airflow is generated where the air flowing through the filter 26 into the radially inner side of the upstream partition wall 20 flows into the first flow-out passage 162 b. At the same time, a second airflow is generated where the air flowing through the filter 26 into the radially outer side of the upstream partition wall 20 flows into the second flow-out passage 162 c.

In the first airflow, the air in the radially inner side of the upstream partition wall 20 flows through the radially inner side of the cylinder portion 141 of the partition cylinder portion 14 and flows along the expanded portion 142 to turn outward in the fan radial direction DRr. The air flowing outward is drawn into the first blowing portion 12 a and then blown out from the first blowing portion 12 a to the first flow-out passage 162 b.

In the second airflow, the air in the radially outer side of the upstream partition wall 20 flows through the radially outer side of the cylinder portion 141 of the partition cylinder portion 14 and flows along the expanded portion 142 to turn outward in the fan radial direction DRr. The air flowing outward is drawn into the second blowing portion 12 b and then blown out from the second blowing portion 12 b to the second flow-out passage 162 c.

In the present embodiment, as shown in FIGS. 1, 2, the length L1 r of the first blade 121 in the fan radial direction DRr is larger than the length L2 r of the second blade 122 in the fan radial direction DRr. The air drawn into the space between the first blades 121 passes through the inner side in the fan radial direction DRr with respect to the partition cylinder portion 14, and the air drawn into the space between the second blades 122 passes through the outer side in the fan radial direction DRr with respect to the partition cylinder portion 14.

Since the airs flow through different ways, the length L1 r of the first blade 121 can be made longer. Accordingly, in order to obtain a specific fan performance, the size of the first blade 121 in the fan axial direction DRa can be made smaller according to the length L1 r of the first blade 121. Accordingly, the size of the blower 10 can be small without deterioration of the performance of the blower 10. That is, it is possible to achieve both compactness and high performance of the blower 10.

According to the present embodiment, the inner diameter D1 i of the first blades 121 whose center is the fan central axis CL is smaller than the inner diameter D2 i of the second blades 122. The air drawn into the space between the first blades 121 flows through the radially inner side of the cylinder portion 141 of the partition cylinder portion 14 in the fan radial direction DRr while the air drawn into the space between the second blades 122 flows through the radially outer side of the cylinder portion 141 of the partition cylinder portion 14.

Accordingly, the length L1 r of the first blade 121 can be increased by utilizing the difference in the air flowing place, and the height of the first blade 121 in the fan axial direction DRa can be decreased without increasing the size of the centrifugal fan 12. In short, it can contribute to miniaturization of the blower 10.

Since the inner diameter D1 i of the first blade 121 is smaller than the inner diameter D2 i of the second blade 122, it is advantageous to secure an opening area of the second air intake port 16 c. That is, since the inner diameter D2 i of the second blade 122 is large, an area of the air passage through which the air flows into the space between the second blades 122 can be secured on the radially outer side of the cylinder portion 141. As a result, the performance of the centrifugal fan 12 can be improved.

According to the present embodiment, the outer diameter D2 o of the second blades 122 whose center is the fan central axis CL is smaller than the outer diameter D1 o of the first blades 121. Accordingly, it is easy to provide a structure that prevents the air from flowing through the gap between the partition panel 18 and the partition panel 123 of the centrifugal fan 12 with avoiding interference between the partition panel 18 and the second blade 122.

It is easy to shape the first blowing portion 12 a into a flat shape in which a ratio of the height of the fan to the fan outer diameter is small without making the inner diameter D1 i of the first blade 121 too small. Accordingly, it is possible to secure the width of the expanded portion 142 in the fan radial direction DRr such that the air flowing around the expanded portion 142 of the partition cylinder portion 14 in the fan axial direction DRa smoothly turns outward in the fan radial direction DRr. Accordingly, the size of the centrifugal fan 12 in the fan axial direction DRa can be decreased while suppressing a deterioration of the performance due to the decrease of the inner diameter D1 i of the first blade 121.

Further, according to the present embodiment, the inward extending part 126 of the centrifugal fan 12 extends inward in the fan radial direction DRr from the radially inner part of the separation panel 123 as shown in FIGS. 1, 2. The inward extending part 126 is located inside in the fan radial direction DRr of both the first end 121 a of the first blade 121 and the second end 122 b of the second blade 122 joined to the separation panel 123. Accordingly, the inward extending part 126 deflects the air to some extent and partitions the air flowing toward the space between the first blades 121 from the air flowing toward the space between the second blades 122 such that the airs are separately drawn into the space between the first blades 121 and the space between the second blades 122.

Accordingly, the mixing of the flow of the air flowing toward the space between the first blades 121 and the flow of the air flowing toward the space between the second blades 122 can be suppressed on the airflow upstream side of the first blades 121 and the second blades 122. This makes it possible to suppress the deterioration of the fan performance of the blower 10.

According to the present embodiment, the centrifugal fan 12 includes the separation panel 123 between the first blades 121 and the second blades 122, and the separation panel 123 has a plate shape extending in the fan radial direction DRr. The separation panel 123 partitions the air flowing through the space between the first blades 121 from the air flowing through the space between the second blades 122.

Accordingly, the separation panel 123 limits the air flowing through the space between the first blades 121 from mixing with the air flowing through the space between the second blades 122. Since the mixing of the airs is suppressed, disturbance of the air caused by the mixing of the airs can be suppressed, and accordingly a decrease in performance of the fan due to the disturbance of the air can be avoided. Further, avoiding the deterioration of the performance of the fan leads to miniaturization of the centrifugal fan 12.

According to the present embodiment, the radially inner part of the separation panel 123 in the fan radial direction DRr is connected to the partition cylinder portion 14. The partition cylinder portion 14 rotates together with the centrifugal fan 12 and extends inward in the fan radial direction DRr from the radially inner part of the separation panel 123. Accordingly, the air flowing on the radially inner side of the partition cylinder portion 14 and the air flowing on the radially outer side of the partition cylinder portion 14 which are separated from each other can be smoothly guided to the first blowing portion 12 a and the second blowing portion 12 b separately. Accordingly, a generation of vortices caused by a gap between the separation panel 123 and the expanded portion 142 of the partition cylinder portion 14 in an imaginary configuration in which the separation panel 123 is spaced from the expanded portion 142 can be avoided. That is, a decrease in performance of the fan caused when the vortices are drawn into the space between the first blades 121 or the space between the second blades 122 can be avoided.

According to the present embodiment, as shown in FIGS. 3, 4, the number of the first blades 121 is different from the number of the second blades 122. Accordingly, the first blades 121 and the second blades 122 need not be continuous in the fan axial direction DRa, and the first blade 121 and the second blade 122 may have different shape. For example, the shapes of the first blade 121 and the second blade 122 may be changed according to the lengths L1 r, L2 r.

According to the present embodiment, as shown in FIG. 3, the first blade 121 is positioned on the side opposite to the fan rotation direction RT toward the outer side in the fan radial direction DRr. The backward-curved blades are suitable for having a flat shape in which the ratio of the height of the fan to the outer diameter is small. Accordingly, the shapes of the first blades 121 are easy to be modified such that the inner diameter D1 i is small and the length L1 r is large.

According to the present embodiment, as shown in FIG. 4, the second blade 122 is the forward-curved blade that is positioned on the forward direction side in the fan rotation direction RT toward the outer side in the fan radial direction DRr. The fan having forward-curved blades is better than the fan having backward-curved blades to modify the fan inner diameter to be large. Accordingly, the shapes of the second blades 122 are suitable to secure the air flow area for the air flowing into the space between the second blades 122. That is, the shapes of the second blades 122 are suitable to secure the opening area of the second air intake port 16 c.

According to the present embodiment, a height HB1 of the first trailing edge 121 d in the fan axial direction DRa is smaller than a height HB2 of the second trailing edge 122 d as shown in FIGS. 1, 2. Accordingly, a space for the first blades 121 in the fan axial direction DRa can be small in addition to securing the air flow area for the air flowing out of the space between the second blades 122.

According to the present embodiment, a height HF1 of the first leading edge 121 c in the fan axial direction DRa is smaller than a height HF2 of the second leading edge 122 c. Accordingly, a space for the first blades 121 in the fan axial direction DRa can be small in addition to securing the air flow area for the air flowing into the space between the second blades 122.

Further, according to the present embodiment, the partition panel 18 partitions the fan surrounding space 162 a into which the air flow from the centrifugal fan 12 into the first flow-out passage 162 b and the second flow-out passage 162 c located on the one side of the first flow-out passage 162 b in the fan axial direction DRa. The first air blown out of the space between the first blades 121 flows into the first flow-out passage 162 b. Simultaneously, the second air blown out of the space between the second blades 122 flows into the second flow-out passage 162 c. The partition panel 18 is provided to suppress the first air from flowing into the second flow-out passage 162 c and to suppress the second air from flowing into the first flow-out passage 162 b.

Accordingly, the airs partitioned by the partition cylinder portion 14 and taken in the centrifugal fan 12 keeps being separated and flow out of the blower 10 from the first flow-out passage 162 b and the second flow-out passage 162 c separately.

Further, according to the present embodiment, the upstream partition wall 20 provided as a member separated from the partition cylinder portion 14 on the one side in the fan axial direction DRa with respect to the cylinder portion 141, and has a cylindrical shape aligned to the cylinder portion 141 in the fan axial direction DRa. The upstream partition wall 20 partitions the air flowing into the inner side of the cylinder portion 141 from the air flowing into the outer side of the cylinder portion 141 on the airflow upstream side of the the cylinder portion 141. The filter 26 filtrating the air flowing toward the centrifugal fan 12 is located on the one side in the fan axial direction DRa with respect to the upstream partition wall 20, and the upstream partition wall 20 extends to the filter 26. Accordingly, the air flowing through the inside of the cylinder portion 141 and the air flowing through the outside of the cylinder portion 141 can be prevented from mixing together between the filter 26 and the partition cylinder portion 14, and the partition cylinder portion 14 can be provided without regard to the shape and the position of the filter 26.

Second Embodiment

A second embodiment of the present disclosure is described next. The present embodiment will be explained primarily with respect to portions different from those of the first embodiment. In addition, explanations of the same or equivalent portions as those in the above embodiment will be omitted or simplified. This also applies to the description of the embodiment to be described later.

As shown in FIG. 5, in the present embodiment, the partition cylinder portion 14 is separated from the centrifugal fan 12. That is, the partition cylinder portion 14 of the present embodiment includes the inward extending part 126 of the centrifugal fan 12. Specifically, the partition cylinder portion 14 is provided such that the expanded portion 142 of the partition cylinder portion 14 is located inside the inward extending part 126 of the centrifugal fan 12 in the fan radial direction DRr. The partition cylinder portion 14 is a non-rotating member that does not rotate.

Further, in the present embodiment, the upstream partition wall 20 (see FIG. 1) is not provided. Instead, the partition cylinder portion 14 extends to the filter 26 located on the one side in the fan axial direction DRa with respect to the partition cylinder portion 14. In detail, the cylinder portion 141 of the partition cylinder portion 14 extends to the filter 26 provided on the one side in the fan axial direction DRa with respect to the cylinder portion 141. This positional relationship between the cylinder portion 141 and the filter 26 is the same as the positional relationship between the upstream partition wall 20 and the filter 26 of the first embodiment.

Since the centrifugal fan 12 rotates while the partition cylinder portion 14 is the non-rotating member in the present embodiment, the partition cylinder portion 14 is slightly separated from the centrifugal fan 12 so as not to interfere with the rotation of the centrifugal fan 12.

The partition cylinder portion 14 separates the air flowing into the space between the first blades 121 from the air flowing into the space between the second blades 122 on the airflow upstream side of the inward extending part 126 of the centrifugal fan 12. That is, the partition cylinder portion 14 is provided relative to the centrifugal fan 12 such that the air flowing along the expanded portion 142 of the partition cylinder portion 14 into the first blowing portion 12 a and the air flowing into the second blowing portion 12 b are limited from mixing together.

For example, the expanded portion 142 of the partition cylinder portion 14 is slightly spaced from the inward extending part 126 of the centrifugal fan 12. Assuming that the partition cylinder portion 14 is provided without the gap between the inward extending part 126 and the expanded portion 142, the partition cylinder portion 14 has a plate shape continuing from the inward extending part 126 to the expanded portion 142. Although less communication of the air through the small gap between the expanded portion 142 of the partition cylinder portion 14 and the inward extending part 126 of the centrifugal fan 12 is better, the communication needs not completely shut off.

Aside from the above described aspects, the present embodiment is the same as the first embodiment. Further, in the present embodiment, effects similar to those of the first embodiment described above can be obtained in the same manner as in the first embodiment.

According to the present embodiment, the partition cylinder portion 14 does not include the inward extending part 126 of the centrifugal fan 12, but the inward extending part 126 extends inward from the separation panel 123 in the fan radial direction DRr. The inward extending part 126 is located inside, in the fan radial direction DRr, both the first end 121 a of the first blade 121 and the second end 122 b of the second blade 122.

The airs partitioned by the partition cylinder portion 14 may mix together through the gap between the expanded portion 142 and the inward extending part 126, and thereby the airflow may be disturbed. In this case, the airflows containing the disturbance and flowing toward the blowing portions 12 a, 12 b are controlled by the inward extending part 126, and then the air flows into the space between the first blades 121 and the space between the second blades 122. As a result, a deterioration of the fan performance due to the mixing of the airs separated from each other on the airflow upstream side of the blades 121, 122 can be suppressed.

According to the present embodiment, the partition cylinder portion 14 is separated from the centrifugal fan 12 and is a non-rotating member that does not rotate. Accordingly, it is easy to simplify the structure of the centrifugal fan 12 to improve the productivity of the blower 10 as compared with a case where the partition cylinder portion 14 is integrated with the centrifugal fan 12, for example.

Further, the filter 26 is located on the one side in the fan axial direction DRa with respect to the partition cylinder portion 14, and the partition cylinder portion 14 extends to the filter 26. Accordingly, the air flowing toward the radially inner side of the cylinder portion 141 and the air flowing toward the radially outer side of the cylinder portion 141 are limited from mixing together on the airflow downstream side of the filter 26 without any object between the filter 26 and the partition cylinder portion 14.

Third Embodiment

A third embodiment is described next. The present embodiment will be explained primarily with respect to portions different from those of the second embodiment.

As shown in FIG. 6, the partition cylinder portion 14 is separated from the centrifugal fan 12 and is a non-rotating member. In this point, the present embodiment is similar to the second embodiment.

However, the partition cylinder portion 14 does not include the inward extending part 126 in the present embodiment. The present embodiment is different from the second embodiment in this point.

Accordingly, the expanded portion 142 of the partition cylinder portion 14 is slightly spaced from the partition cylinder portion 123 of the centrifugal fan 12. Assuming that the partition cylinder portion 14 is provided without the gap between the partition cylinder portion 123 and the expanded portion 142, the partition cylinder portion 14 has a plate shape continuing from the partition cylinder portion 123 to the expanded portion 142. Although less communication of the air through the small gap between the expanded portion 142 of the partition cylinder portion 14 and the partition cylinder portion 123 of the centrifugal fan 12 is better, the communication needs not completely shut off.

Aside from the above described aspects, the present embodiment is the same as the second embodiment. Further, in the present embodiment, effects similar to those of the second embodiment described above can be obtained in the same manner as in the second embodiment.

Other Embodiments

(1) In the above-described embodiments, the centrifugal fan 12 includes the first blades 121 and the second blades 122 as shown in FIG. 1, for example, but this is just an example. For example, the centrifugal fan 12 may include multiple third blades and multiple fourth blades aligned to the blades 121, 122 in the fan axial direction DRa in addition to the blades 121, 122. That is, the fan 12 may include multiple blowing portions having multiple blades, and the multiple blowing portions may be aligned in the fan axial direction DRa. (2) In the above-described embodiments, the shape of the turbofan is used as the shape of the first blade 121 as shown in FIG. 3. However, this is just an example. For example, another shape of a centrifugal fan different from the shape of the turbofan may be used as the shape of the first blade 121. (3) In the above-described embodiments, the shape of the sirocco fan is used as the shape of the second blade 122 as shown in FIG. 4. However, this is just an example. For example, another shape of a centrifugal fan different from the shape of the sirocco fan may be used as the shape of the second blade 122. (4) In the above-described embodiments, the filter 26 is located on the airflow upstream side of the centrifugal fan 12 as shown in FIG. 1, for example. However, the filter 26 may not be provided. (5) In the above-described embodiments, the number of the first blades 121 is smaller than the number of the second blades 122 as shown in FIGS. 3, 4. However, this is just an example. For example, the number of the first blades 121 may be equal to or larger than the number of the second blades 122. (6) In the above-described embodiments, the centrifugal fan 12 includes the separation panel 123 as shown in FIG. 1, for example. However, the separation panel 123 may not be provided. For example, assuming that the blower 10 of the third embodiment shown in FIG. 6 does not include the separation panel 123, the first blades 121 and the second blades 122 are directly connected with each other as shown in FIG. 7. (7) The present disclosure is not limited to the specific embodiments described above, and various modifications can be made. In each of the above embodiments, it is needless to say that the elements configuring the embodiment are not necessarily indispensable except when it is clearly indicated that the elements are particularly indispensable, when the elements are clearly considered to be indispensable in principle, and the like.

Further, in each of the above embodiments, when numerical values such as the number, numerical value, quantity, range, and the like of the components of the embodiment are referred to, except in the case where the numerical value is expressly indispensable in particular, the case where the numerical value is obviously limited to a specific number in principle, and the like, the present disclosure is not limited to the specific number. Furthermore, a material, a shape, a positional relationship, or the like, if specified in the above-described example embodiments, is not necessarily limited to the specific material, shape, positional relationship, or the like unless it is specifically stated that the material, shape, positional relationship, or the like is necessarily the specific material, shape, positional relationship, or the like, or unless the material, shape, positional relationship, or the like is obviously necessary to be the specific material, shape, positional relationship, or the like in principle.

CONCLUSION

According to a first aspect described in all or some of the above-described embodiments, the centrifugal fan includes the first blades and the second blades which are arranged about the fan central axis. The second blades located on the one side of the first blades in the axial direction of the fan central axis. The air passing through the radially inner side of the partition cylinder portion is taken into the spaces between the first blades, and the air passing through the radially outer side of the partition cylinder portion is taken into the spaces between the second blades. The partition cylinder portion partitions, on the airflow upstream side of the first blades and the second blades, the air taken into the spaces between the first blades from the air taken into the spaces between the second blades. The length of the first blades in the radial direction is larger than the length of the second blades in the radial direction.

As described above, the length of the first blades in the radial direction is larger than the length of the second blades in the radial direction. Accordingly, in order to obtain a specific fan performance, the size of the first blade in the axial direction can be decreased according to the increase of the length of the first blade. Accordingly, the size of the centrifugal blower can be small without deterioration of the performance of the centrifugal blower.

According to a second aspect, the inner diameter of the first blades whose center is the fan central axis is smaller than the inner diameter of the second blades. The air drawn into the space between the first blades flows through the radially inner side of the partition cylinder portion in the radial direction while the air drawn into the space between the second blades flows through the radially outer side of the partition cylinder portion. Accordingly, the length of the first blade can be increased by utilizing the difference in the air flowing place, and the height of the first blade in the axial direction can be decreased without increasing the size of the centrifugal fan. In short, it can contribute to miniaturization of the centrifugal blower.

That is, since the inner diameter of the second blade is large, an area of the air passage through which the air flows into the space between the second blades can be secured on the radially outer side of the partition cylinder portion. As a result, the performance of the centrifugal fan can be improved.

According to a third aspect, the outer diameter of the second blades whose center is the fan central axis is smaller than the outer diameter of the first blades.

According to a fourth aspect, the centrifugal fan has the separation panel located between the first blades and the second blades. The separation panel has a plate shape extending in the radial direction. The separation panel partitions the air flowing through the space between the first blades from the air flowing through the space between the second blades. Accordingly, the separation panel limits the air flowing through the space between the first blades from mixing with the air flowing through the space between the second blades.

According to a fifth aspect, the radially inner part of the separation panel in the radial direction is connected to the partition cylinder portion. The partition cylinder portion rotates together with the centrifugal fan and extends inward in the radial direction from the radially inner part of the separation panel. Accordingly, the air flowing on the radially inner side of the partition cylinder portion and the air flowing on the radially outer side of the partition cylinder portion which are separated from each other can be smoothly guided to the first blades and the second blades. Accordingly, a generation of vortices caused by a gap between the separation panel and the partition cylinder portion in an imaginary configuration in which the separation panel is spaced from the partition cylinder portion can be avoided. That is, a decrease in performance of the fan caused when the vortices are drawn into the space between the first blades or the space between the second blades can be avoided.

According to a sixth aspect, the partition cylinder portion is separated from the centrifugal fan and is a non-rotating member that does not rotate. Accordingly, it is easy to simplify the structure of the centrifugal fan to improve the productivity of the centrifugal blower as compared with a case where the partition cylinder portion is integrated with the centrifugal fan, for example.

According to a seventh aspect, the number of the first blades is different from the number of the second blades. Accordingly, the first blades and the second blades need not be continuous in the axial direction, and the first blade and the second blade may have different shape. For example, the shapes of the first blade and the second blade may be changed according to the lengths.

According to an eighth aspect, the first blade is a backward-curved blade extending away from a rotation direction of the centrifugal fan toward the outer side of the first blade in the radial direction. The backward-curved blades are suitable for having a flat shape in which the ratio of the height of the fan to the outer diameter is small. Accordingly, the shapes of the first blades are easy to be modified such that the inner diameter is small and the length is large.

According to a ninth aspect, the second blade is a forward-curved blade extending toward the rotation direction of the centrifugal fan toward the outer side of the second blade. The fan having forward-curved blades is better than the fan having backward-curved blades to modify the fan inner diameter to be large. Accordingly, the shapes of the second blades are suitable to secure the air flow area for the air flowing into the space between the second blades.

According to a tenth aspect, each of the second blades has a second trailing edge that is a downstream edge located downstream with respect to the airflow in the space between the second blades. Each of the second blades has a second trailing edge that is a downstream edge located downstream with respect to the airflow in the space between the second blades. The height of the first trailing edge is larger than the height of the second trailing edge in the axial direction. Accordingly, a space for the first blades in the axial direction can be small in addition to securing the air flow area for the air flowing out of the space between the second blades.

According to an eleventh aspect, each of the second blades has the second leading edge that is an upstream edge located downstream with respect to the airflow in the space between the second blades. Each of the second blades has a second leading edge that is an upstream edge located upstream with respect to the airflow in the space between the second blades. The height of the first leading edge is larger than the height of the second leading edge in the axial direction. Accordingly, a space for the first blades in the axial direction can be small in addition to securing the air flow area for the air flowing into the space between the second blades.

According to an eleventh aspect, the fan casing that accommodates the centrifugal fan defines the fan surrounding space that surrounds the centrifugal fan on the radially outside. The air flows out of the centrifugal fan into the fan surrounding space. The partition panel partitions the fan surrounding space in the axial direction into the first flow-out passage and the second flow-out passage. The first air blown out of the space between the first blades flows into the first flow-out passage. In contrast, the second air blown out of the space between the second blades flows into the second flow-out passage. The partition panel is provided to suppress the first air from flowing into the second flow-out passage and to suppress the second air from flowing into the first flow-out passage. Accordingly, the air partitioned by the partition cylinder portion and taken in the centrifugal fan keeps being separated and flows out of the centrifugal blower from the first flow-out passage and the second flow-out passage separately.

According to a thirteenth aspect, the filter that filtrates the air flowing toward the centrifugal fan is located on the one side of the partition cylinder portion in the axial direction. The partition cylinder portion extends to the filter. Accordingly, the air flowing toward the radially inner side of the partition cylinder portion and the air flowing toward the radially outer side of the partition cylinder portion are limited from mixing together on the airflow downstream side of the filter.

According to a fourteenth aspect, the upstream partition wall is separated from the partition cylinder portion and located on the one side of the partition cylinder portion in the axial direction. The upstream partition wall has a cylindrical shape aligned to the partition cylinder portion in the axial direction. The upstream partition wall partitions the air flowing into the inner side of the partition cylinder portion from the air flowing into the outer side of the partition cylinder portion on the airflow upstream side of the partition cylinder portion. The filter filtrating the air flowing toward the centrifugal fan is located on the one side in the axial direction with respect to the upstream partition wall, and the upstream partition wall extends to the filter. In this configuration also, similarly to the thirteenth aspect, the air flowing toward the radially inner side of the partition cylinder portion and the air flowing toward the radially outer side of the partition cylinder portion are limited from mixing together on the airflow downstream side of the filter.

Although the present disclosure has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.

Additional advantages and modifications will readily occur to those skilled in the art. The disclosure in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. 

What is claimed is:
 1. A centrifugal blower comprising: a centrifugal fan including a plurality of first blades arranged about a fan central axis, and a plurality of second blades arranged about the fan central axis, the plurality of second blades being located on a first side of the plurality of first blades in an axial direction of the fan central axis and being aligned to the plurality of first blades; and a partition cylinder portion having a cylindrical shape extending in the axial direction, a diameter of the partition cylinder portion expanding in the axial direction toward a second side that is an opposite side of the first side, the partition cylinder portion being located inside the plurality of second blades in a radial direction of the centrifugal fan, wherein the centrifugal fan is configured to rotate about the fan central axis to take in air from the first side into spaces between the plurality of first blades and spaces between the plurality of second blades, blow out the air in the spaces between the plurality of first blades outward in the radial direction, and blow out the air in the spaces between the plurality of second blades outward in the radial direction, the partition cylinder portion partitions, on an airflow upstream side of the plurality of first blades and the plurality of second blades, the air taken into the spaces between the plurality of first blades through an inside of the partition cylinder portion in the radial direction from the air taken into the spaces between the plurality of second blades through an outside of the partition cylinder portion in the radial direction, and a length of each first blade of the plurality of first blades in the radial direction is larger than a length of each second blade of the plurality of second blades in the radial direction.
 2. The centrifugal blower according to claim 1, wherein an inner diameter of the plurality of first blades whose center is the fan central axis is smaller than an inner diameter of the plurality of second blades whose center is the fan central axis.
 3. The centrifugal blower according to claim 1, wherein an outer diameter of the plurality of second blades whose center is the fan central axis is smaller than an outer diameter of the plurality of first blades whose center is the fan central axis.
 4. The centrifugal blower according to claim 1, wherein the centrifugal fan includes a separation panel located between the plurality of first blades and the plurality of second blades, the separation panel having a plate shape extending in the radial direction, wherein the separation panel partitions the air flowing through the spaces between the plurality of first blades from the air flowing through the spaces between the plurality of second blades.
 5. The centrifugal blower according to claim 4, wherein a radially inner part of the separation panel in the radial direction is joined to the partition cylinder portion, the partition cylinder portion is configured to rotate together with the centrifugal fan, and the partition cylinder portion extends inward in the radial direction from the separation panel.
 6. The centrifugal blower according to claim 1, wherein the partition cylinder portion is separated from the centrifugal fan and is a non-rotating member that is not configured to rotate.
 7. The centrifugal blower according to claim 1, wherein a number of the plurality of first blades is different from a number of the plurality of second blades.
 8. The centrifugal blower according to claim 1, wherein the each first blade is a backward-curved blade extending away from a rotation direction of the centrifugal fan toward an outer side of the each first blade in the radial direction.
 9. The centrifugal blower according to claim 1, wherein the each second blade is a forward-curved blade extending toward a rotation direction of the centrifugal fan toward an outer side of the each second blade in the radial direction.
 10. The centrifugal blower according to claim 1, wherein the each first blade has a first trailing edge located downstream in the each first blade with respect to an airflow in the spaces between the plurality of first blades, the each second blade has a second trailing edge located downstream in the each second blade with respect to an airflow in the spaces between the plurality of second blades, and a height of the first trailing edge in the axial direction is smaller than a height of the second trailing edge in the axial direction.
 11. The centrifugal blower according to claim 1, wherein the each first blade has a first leading edge located upstream in the each first blade with respect to an airflow in the spaces between the plurality of first blades, the each second blade has a second leading edge located upstream in the each second blade with respect to an airflow in the spaces between the plurality of second blades, and a height of the first leading edge in the axial direction is smaller than a height of the second leading edge in the axial direction.
 12. The centrifugal blower according to claim 1, further comprising: a fan casing that accommodates the centrifugal fan, the fan casing defining a fan surrounding space that surrounds the centrifugal fan outside the centrifugal fan in the radial direction, the air flowing into the fan surrounding space from the centrifugal fan; and a partition panel that partitions the fan surrounding space in the axial direction into a first flow-out passage and a second flow-out passage, wherein a first air flowing out of the spaces between the plurality of first blades flows into the first flow-out passage, a second air flowing out of the spaces between the plurality of second blades flows into the second flow-out passage, and the partition panel is configured to limit the first air from entering the second flow-out passage and limit the second air from entering the first flow-out passage.
 13. The centrifugal blower according to claim 1, further comprising: a filter located on a first side of the partition cylinder portion in the axial direction to filtrate the air flowing toward the centrifugal fan, wherein the partition cylinder portion extends to the filter.
 14. The centrifugal blower according to claim 1, further comprising: an upstream partition wall located on a first side of the partition cylinder portion in the axial direction and separated from the partition cylinder portion, the upstream partition wall having a cylindrical shape aligned to the partition cylinder portion in the axial direction, the upstream partition wall partitioning the air flowing into the inside of the partition cylinder portion from the air flowing into the outside of the partition cylinder portion on an airflow upstream side of the partition cylinder portion; and a filter located on a first side of the upstream partition wall in the axial direction to filtrate the air flowing toward the centrifugal fan, wherein the upstream partition wall extends to the filter. 